Ghosts in pure and hybrid formalisms of gravity theories: a unified analysis

Abstract

In the first order formalism of gravitational theories, the spacetime connection is considered as an independent variable to vary together with the metric. However, the metric still generates its Levi-Civita connection that turns out to determine the geodesics of matter. Recently, "hybrid" gravity theories have been introduced by constructing actions involving both the independent Palatini connection and the metric Levi-Civita connection. In this study a method is developed to analyse the field content of such theories, in particular to determine whether the propagating degrees of freedom are ghosts or tachyons. New types of second, fourth and sixth order derivative gravity theories are investigated and the so called f(X) theories are singled out as a viable class of "hybrid" extensions of General Relativity.

9 pages

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Cited by in corpus (25)

• Born-Infeld inspired modifications of gravity
• Hybrid metric-Palatini gravity
• Ghosts in metric-affine higher order curvature gravity
• Instabilities in Metric-Affine Theories of Gravity
• Einstein static Universe in hybrid metric-Palatini gravity
• Galactic rotation curves in hybrid metric-Palatini gravity
• Cosmological solutions in generalized hybrid metric-Palatini gravity
• A dynamical system analysis of hybrid metric-Palatini cosmologies
• Beyond Einstein's General Relativity: Hybrid metric-Palatini gravity and curvature-matter couplings
• The Cosmology of Interacting Spin-2 Fields
• The Cauchy problem in hybrid metric-Palatini f(X)-gravity
• Scalar modes in extended hybrid metric-Palatini gravity: weak field phenomenology
• Sudden singularities in generalized hybrid metric-Palatini cosmologies
• Geometric Proca with Matter in Metric-Palatini Gravity
• Weak-field regime of the generalized hybrid metric-Palatini gravity
• Black Hole Perturbations and Quasinormal Modes in Hybrid Metric-Palatini Gravity
• Cosmic strings in generalized hybrid metric-Palatini gravity
• Complete density perturbations in the Jordan-Fierz-Brans-Dicke theory
• Dynamical reconstruction of the $\Lambda$CDM model in hybrid metric-Palatini gravity
• Unscreening scalarons with a black hole
• Novel aspects of C-theories in Cosmology
• Polarization and speed of gravitational waves in hybrid metric-Palatini f(R)-gravity
• Novel electrically charged wormhole, black hole and black bounce exact solutions in hybrid metric-Palatini gravity
• Non-minimal scalar-tensor theories
• Gravitational wave propagation in generalized hybrid metric-Palatini gravity